Stunning 3D Rock Images Revealed in New Lab

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PRINCETON, N.J. — A geologist and an architect standing in a lab
may sound like the start to a very nerdy joke, but a pair of
these professionals have joined together to revolutionize the way
scientists study structures, such as fossils, inside rocks.

Geologists use a variety of techniques to analyze fossils and
other
features trapped inside Earth's rocky layers. The most basic
technique, dating back to the 19th century, involves slicing away
layers of rock, taking pictures of each layer, and then
recreating the full 3D shapes by connecting the dots between
images. But this method is tedious and prone to human error.

"People have done this since Darwin," said Adam Maloof, a
geoscientist at Princeton University who recently opened a rock
imaging lab that brings this technique into the 21st century.
"You can find very old articles from the 1870s where people
sliced something five times, and then drew it, and put together a
model of it."

Researchers have since devised more precise methods using
electronic rock grinders and
digital cameras, but, until now, the technique has not been
automated.

Revolutionary redesign

Maloof has teamed up with architects at the Brooklyn-based Situ
Studio to design a machine that automatically grinds layers as
thin as 0.00025 centimeters — thinner than a human hair — and
automatically takes high-resolution images along the way.

The grinding setup looks a bit like a mini car wash. On an
automated steel shuttle, the rock first travels under misting
nodules that clean away grime. Next, the rock passes back and
forth under a 1-inch-thick (2.5 cm) diamond-studded grinding
wheel, with a stream of water flowing to reduce dust. The sample
then exits the grinder under a series of wiper blades and enters
the limelight of an automated camera that snaps a shot from
above. The shuttle then returns the rock to the start position,
where the process repeats. [ See
photos of the lab and 3D rock models ]

Maloof wears mist-covered safety goggles as he describes the
special features of the room: Double-width cinder blocks in the
walls help reduce sound pollution outside, and a climate control
system maintains a constant room temperature.

"The main source of error with a grinder like this is the
expansion and contraction of the steel," Maloof said, with the
machine humming loudly behind him, and all of lights shut off
except a beam glowing from the camera area. "If you have
temperature fluctuations at night, for example, the steel will
change size and there will be an error."

Even the slightest shift can cause images to misalign and
jeopardize the precision of the digital model.

The machine hums along day and night, and can grind through
several inches of rock within 24 hours. A modern manual setup
would take up to two weeks to cover the same area, and would not
be as accurate.

Ancient life

Maloof's interest in high-precision grinding was sparked in 2009
when he and his graduate students discovered what they thought
could be
the earliest evidence of fossilized animal life. In a
640-million-year-old rock formation in South Australia, the team
found large patches of small red flakes that varied in size and
shape, and looked nothing like the surrounding rock. The group
brought samples back to Princeton, where they spent two weeks
manually grinding and imaging about half an inch (1.5 cm) of
sample. [ Photos:
The World's Most Famous Rocks ]

With the help of Situ Studio, the group created a 3D model of
their manual images and found what seemed to be remnants of
ancient marine sponges. The team hopes to confirm this
finding with their improved system.

"It definitely points to the potentials of interdisciplinary
work," said Brad Samuels of Situ Studio, who helped Maloof choose
the appropriate imaging and coding software, similar to what
architects use to plan buildings. "The kinds of things that they
needed in terms of tools and work flow are things that we have as
a studio that we employ in designing spaces."

Oil drilling and meteorite dissection

A number of collaborators have already contacted Maloof about
using the lab, including geologists in the oil industry wanting
to analyze potential drilling rock, and geophysicists interested
in dissecting meteorites.

"This is a very exciting instrument," said Roger Fu, a geophysics
graduate student at MIT who will travel to the lab later this
summer to study structures
within meteorites that could help reveal information about
how the solar system formed. "With the grinder, we should be
able to get better 3D maps of meteorites than ever before."

A downside of the grinder is that it ultimately destroys the
sample, Fu said. Some researchers avoid this by using X-ray
scanning technology to peer inside rocks, but X-rays blur with
depth, and do not differentiate between different materials of
the same density.

For now, Maloof is working out the final kinks of the system
using less valuable samples. The results, so far, have produced
stunningly beautiful images of structures inside rocks.

"If you looked at these with an X-ray, you would see absolutely
nothing," Maloof said, pointing to an image of sand grains coated
in concentric layers of calcium carbonate.

The compiled images of this rock reveals the full spherical form
of each sand grain for the first time since they fused together
hundreds of millions of years ago.

Editor's Note: The author
worked with Maloof's research group in 2010 and 2011 as a lab
technician, and helped collect some of the fossil rocks from
South Australia. She was not, however, involved in the analysis
of the rock.